The blood test, developed by Iranian doctors and backed by the World Health Organization, measures levels of a hormone produced by the ovaries.

The anti-mullerian hormone (AMH) can be tested in women as young as 20 to establish when they will no longer be able to have babies.

Researchers say the test is accurate to within a few months.

The 12-year study involved taking blood samples from 266 women at intervals of three years.

The women were aged between 20 and 49 and they also underwent physical examinations every three years.

Family planning

Research leader Dr Fahimeh Ramezani Tehrani says the test will be a boon for women who want to plan when to start a family.

"Menopause occurs in a wide range from 40 to 60 years but about 5% of women are at risk of early menopause - meaning being menopausal at an age less than 45," she says.

"For that reason I think that it is an issue that is important for any woman, because menopause is a milestone in women's reproductive life."

Tehrani says the test will target many different women.

"Nowadays women try to postpone their fertility and their child-bearing because they would like to finish their education, get a good opportunity for working and for that reason the age of first pregnancy is increased," she said.

"Fertility is reduced between two or three years before menopause. If you have an estimate for age of menopause then you can estimate the age of your fertility."

Tehrani says the test is accurate.

"We believe that it is accurate because when we check the estimated age of menopause based on this age with the actual age of menopause for those women who reach menopause during our study, we find they are very similar," she says.

"[There is] only four months difference between the estimated age and the actual age."

Doctors can already tell a woman if she is close to menopause but this is the first time scientists have worked out a formula for linking AMH levels in younger women to future age of infertility.

After testing the study on a wider sample, it is expected to be made widely available within two years.

'Unrealistic'

But IVF Australia is doubtful about the test's ability to make such accurate predictions about fertility and menopause.

"I'm a little sceptical given that it is a statistical model rather than working on real patients and following them through to menopause," he says.

"Certainly our data from IVF Australia would suggest that very low levels are very negative in relation to the onset of menopause in the next year or two, but certainly getting down to months and pinpointing it is, I think, a little unrealistic for one biological test.

Chapman says in a fertility sense, it is not particularly useful to pinpoint the onset of menopause.

"What a low level does tell us is we need to get on and try a treatment as soon as possible because we know that menopause will be coming, but exactly when they will be is not sure," he says.

"But it certainly enables us to have a sensible discussion with a woman about whether she should be moving quickly onto fertility treatment, so it does have a use."